1. Field of the Invention
The present invention relates to steel wires for reinforcing rubber, and also to a method of manufacturing the same.
2. Description of the Related Art
Steel radial tires, steel-wire reinforced conveyer belts, steel-wire reinforced timing belts, steel-wire reinforced hoses, steel-wire reinforced handrails, and the like each comprise a rubber member and steel wires or steel cords (made by twisting the steel wires) embedded in the rubber member. The surfaces of the steel wires must be kept clean before they are embedded in the rubber member, otherwise they will greatly impair the corrosion resistance of the wires and the wire-rubber adhesion strength.
To have their surfaces kept clean, the wires are sealed within polyethylene bags, along with dehydrator and nitrogen gas, before they are delivered to the manufacturers of steel radial tires and other steel-wire reinforced products. It is relatively expensive to package the steel wires in this way. Further, the steel wires, thus packaged, can rarely remain sufficiently clean up until the time they are embedded in the rubber members. Consequently, the rubber products reinforced with these steel wires, such as steel radial tires, fail to have adequate wire-rubber adhesion strength, heat resistance, oil resistance, or water resistance.
As is known in the art, once it is surface-treated with triazine-thiol derivatives, a metal member has good corrosion resistance and can adhere firmly to rubber. Various methods of treating the surfaces of wires with triazine-thiol derivatives are disclosed in, for example, Kunio Mori, Functionalization of Metal Surfaces by Triazine Thiols, Practice of Surface Treatment, Vol. 35, No. 5, pages 210-218 (1988) (1989), Published Examined Japanese Patent Application No. 60-41084, and Published Unexamined Japanese Patent Application No. 58-87034. In these methods, the wires are immersed in a solution prepared by dissolving a triazine-thiol derivative in either water or an organic solvent, thereby adsorbing the triazine-thiol derivative on the surface of each wire.
With the conventional surface-treating methods described above, however, it is necessary to immerse the wires in the solution at a relatively high temperature for a long period of time. Further, the layer of triazine-thiol derivative formed on the surface of each wire is not sufficiently dense. Hence, the rubber products reinforced by the wires, thus treated, cannot be said to be adequately resistant to heat, water, steam, or fatigue. All the conventional methods are batch processes, and not suitable for mass-producing steel wires for reinforcing rubber products.